I ran into this problem on my server on wich i play on my own. I had a few fences with animals in them, decided to move those because i was goingt to build there. So, after i broke down all the fences i tried placing some blocks, it just wouldn't let me. I can however, place flowers and such.
It's not chunk related, it's happening withing 3-4 chunks at random spots and its 2 blocks high, wich makes sense to me since i had a fence there.
Using the /fill command works fine to fill those spots, wich does not make sense to me
The only Plugin im using is mcmmo.
i just rechecked, its not necessarily where the fences were, also were i had the cows and sheep